Re: [GHC] #13615: Nondeterminism in ‘pure’ function w/ parallel evaluation & memo combinators

[GHC]

#13615: Nondeterminism in ‘pure’ function w/ parallel evaluation & memo combinators
-------------------------------------+-------------------------------------
        Reporter:  pacak             |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by dfeuer):

 I've written a [https://github.com/treeowl/unordered-containers/tree
 /super-safe seriously legitimate modification] of
 `Data.HashMap.Strict.fromListWith` that Ben indicates still demonstrates
 the problem. This version uses a separate type of mutable hashmap that
 holds `MArray`s. When it's done, it traverses the tree and (unsafely)
 freezes all the arrays. Unless I've goofed up, there should be no doubt
 that this version should work correctly.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13615#comment:37>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler